[ { "id": "authors:9yth2-pjk85", "collection": "authors", "collection_id": "9yth2-pjk85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150204-080936995", "type": "article", "title": "Seismology on Mars", "author": [ { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" }, { "family_name": "Miller", "given_name": "W. F.", "clpid": "Miller-W-F" }, { "family_name": "Latham", "given_name": "G. V.", "clpid": "Latham-G-V" }, { "family_name": "Nakamura", "given_name": "Y.", "clpid": "Nakamura-Y" }, { "family_name": "Toks\u00f6z", "given_name": "M. N.", "clpid": "Toks\u00f6z-M-N" }, { "family_name": "Dainty", "given_name": "A. M.", "clpid": "Dainty-A-M" }, { "family_name": "Duennebier", "given_name": "F. K.", "clpid": "Duennebier-F-K" }, { "family_name": "Lazarewicz", "given_name": "A. R.", "clpid": "Lazarewicz-A-R" }, { "family_name": "Kovach", "given_name": "R. L.", "clpid": "Kovach-R-L" }, { "family_name": "Knight", "given_name": "T. C. D.", "clpid": "Knight-T-C-D" } ], "abstract": "A three-axis short-period seismometer has been operating on the surface of Mars in the Utopia Planitia region since September 4, 1976. During the first 5 months of operation, approximately 640 hours of high quality data, uncontaminated by lander or wind noise, have been obtained. The detection threshold is estimated to be magnitude 3 to about 200 km and about 6.5 for the planet as a whole. No large events\nhave been seen during this period, a result indicating that Mars is less seismically active than earth. Wind is the major source of noise during the day, although the noise level was at or below the sensitivity threshold of the seismometer for most of the night during the early part of the mission. Winds and therefore the seismic background started to intrude into the nighttime hours starting on sol 119 (a sol is a\nMartian day). The seismic background correlates well with wind velocity and is proportional to the square of the wind velocity, as is appropriate for turbulent flow. The seismic envelope power spectral density is proportional to frequency to the -0.66 to -0.90 power during windy periods. A possible local seismic event was detected on sol 80. No wind data were obtained at the time, so a wind disturbance\ncannot be ruled out. However, this event has some unusual characteristics and is similar to local events\nrecorded on earth through a Viking seismometer system. If it is interpreted as a natural seismic event, it\nhas a magnitude of 3 and a distance of 110 km. Preliminary interpretation of later arrivals in the signal\nsuggest a crustal thickness of 15 km at the Utopia Planitia site which is within the range of crustal models\nderived from the gravity field. More events must be recorded before a firm interpretation can be made of\nseismicity or crustal structure. One firm conclusion is that the natural background noise on Mars is low\nand that the wind is the prime noise source. It will be possible to reduce this noise by a factor of 10^3 on\nfuture missions by removing the seismometer from the lander, operation of an extremely sensitive\nseismometer thus being possible on the surface.", "doi": "10.1029/JS082i028p04524", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1977-09-30", "series_number": "28", "volume": "82", "issue": "28", "pages": "4524-4546" }, { "id": "authors:0q16n-xca54", "collection": "authors", "collection_id": "0q16n-xca54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130906-105051343", "type": "article", "title": "Seismology on Mars", "author": [ { "family_name": "Anderson", "given_name": "D. L.", "clpid": "Anderson-D-L" }, { "family_name": "Miller", "given_name": "W. F.", "clpid": "Miller-W-F" }, { "family_name": "Latham", "given_name": "G. V.", "clpid": "Latham-G-V" }, { "family_name": "Nakamura", "given_name": "Y.", "clpid": "Nakamura-Y" }, { "family_name": "Toksoz", "given_name": "M. N.", "clpid": "Toks\u00f6z-M-N" }, { "family_name": "Dainty", "given_name": "A. M.", "clpid": "Dainty-A-M" }, { "family_name": "Duennebier", "given_name": "F. K.", "clpid": "Duennebier-F-K" }, { "family_name": "Lazarewicz", "given_name": "A. R.", "clpid": "Lazarewicz-A-R" }, { "family_name": "Kovach", "given_name": "R. L.", "clpid": "Kovach-R-L" }, { "family_name": "Knight", "given_name": "T. C. D.", "clpid": "Knight-T-C-D" } ], "abstract": "A three-axis short period seismometer has been operating on the surface of Mars in the Utopia\nPlanitia region since September 4, 1976. During the first five months of operation approx. 640\nhours of high quality data, uncontaminated by Lander or wind noise, have been obtained. The\ndetection threshold is estimated to be magnitude 3 to about 200 km and about 6.5 for the planet\nas a whole. No large events have been seen during this period indicating that Mars is less seismically\nactive than Earth.", "doi": "10.1029/EO058i008p00681", "issn": "0002-8606", "publisher": "American Geophysical Union", "publication": "Transactions - American Geophysical Union", "publication_date": "1977-08", "series_number": "8", "volume": "58", "issue": "8", "pages": "828-828" }, { "id": "authors:edtqs-xps76", "collection": "authors", "collection_id": "edtqs-xps76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150218-103157469", "type": "article", "title": "The Viking Seismic Experiment", "author": [ { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" }, { "family_name": "Duennebier", "given_name": "Frederick K.", "clpid": "Duennebier-F-K" }, { "family_name": "Latham", "given_name": "Gary V.", "clpid": "Latham-G-V" }, { "family_name": "Toks\u00f6z", "given_name": "M. Fafi", "clpid": "Toks\u00f6z-M-F" }, { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Knight", "given_name": "Tony C. D.", "clpid": "Knight-T-C-D" }, { "family_name": "Lazarewicz", "given_name": "Andrew R.", "clpid": "Lazarewicz-A-R" }, { "family_name": "Miller", "given_name": "Wayne F.", "clpid": "Miller-W-F" }, { "family_name": "Nakamura", "given_name": "Yosio", "clpid": "Nakamura-Y" }, { "family_name": "Sutton", "given_name": "George", "clpid": "Sutton-G" } ], "abstract": "A three-axis short-period seismometer is now operating on Mars in the Utopia Planitia region. The noise background correlates well with wind gusts. Although no quakes have been detected in the first 60 days of observation, it is premature to draw any conclusions about the seismicity of Mars. The instrument is expected to return data for at least 2 years.", "doi": "10.1126/science.194.4271.1318", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1976-12-17", "series_number": "4271", "volume": "194", "issue": "4271", "pages": "1318-1321" }, { "id": "authors:z4p8c-5ra60", "collection": "authors", "collection_id": "z4p8c-5ra60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:AHRjap71", "type": "article", "title": "Explosive Gas Blast: The Expansion of Detonation Products in Vacuum", "author": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Allen", "given_name": "Charles F.", "clpid": "Allen-C-F" }, { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" } ], "abstract": "A series of 0.2- to 3-gm HNS charges were detonated in vacuums of 10^\u22123 to 10^\u22125 Torr. The resultant freely expanding, detonation product, gas blast achieves terminal velocities of 8 to 12 km/sec within 3 to 5 \u00b5sec after the detonation wave arrives at the free surface. Measured pressure profiles display rise times to maximum stagnation (``reflected shock'') pressure varying from ~30 \u00b5sec, 20-cm away from a 2.6-gm charge, to ~185 \u00b5sec, 127-cm away from 0.2-gm charge at 10\u22125 Torr. Rise times were generally shorter at 10\u22123 and 10\u22124 Torr; the 10\u22125 Torr values agree with numerical calculations. Using cube root scaling of charge mass, the observed peak reflected pressure as a function of range may be represented by\n\np = 6.5 x 10^5 (bar) r'^-3.5,\n\nwhere r[prime] the ratio of the range to the equivalent charge radius.", "doi": "10.1063/1.1660099", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1971-02", "series_number": "2", "volume": "42", "issue": "2", "pages": "815-829" }, { "id": "authors:j649f-fwa84", "collection": "authors", "collection_id": "j649f-fwa84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150708-103900362", "type": "article", "title": "Explosive Seismic Sources for the Moon", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "abstract": "The coupling of seismic energy under vacuum conditions, such as the moon, using an untamped surface charge is different from coupling in air. In vacuum, the explosive gas blast and the detonation products continuously expand out ward and interact with the solid surface. A series of model experiments was performed to investigate the effect\nof vacuum on coupling seismic energy.", "doi": "10.1190/1.1440079", "issn": "0016-8033", "publisher": "Society of Exploration Geophysicists", "publication": "Geophysics", "publication_date": "1970-02-01", "series_number": "1", "volume": "35", "issue": "1", "pages": "33-44" }, { "id": "authors:vx3yt-76a73", "collection": "authors", "collection_id": "vx3yt-76a73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140430-082556595", "type": "article", "title": "Universal dispersion tables III. Free oscillation variational parameters", "author": [ { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" }, { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" } ], "abstract": "The effect of a small change in any parameter of a realistic Earth model on the periods of free oscillation is computed for both spheroidal and torsional modes. The normalized partial derivatives, or variational parameters, are given as a function of order number and depth in the Earth. For a given mode it can immediately be seen which parameters and which regions of the Earth are controlling the period of free oscillation. Except for _oS_o and its overtones the low-order free oscillations are relatively insensitive to properties of the core. The shear velocity of the mantle is the dominant parameter controlling the periods of free oscillation and density can be determined from free oscillation data only if the shear velocity is known very accurately. Once the velocity structure is well known free oscillation data can be used to modify the average density of the upper mantle. The mass and moment of inertia are then the main constraints on how the mass must be redistributed in the lower mantle and core.", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "1969-08-01", "series_number": "4", "volume": "59", "issue": "4", "pages": "1667-1693" }, { "id": "authors:6exyb-gsn97", "collection": "authors", "collection_id": "6exyb-gsn97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141008-150614661", "type": "article", "title": "Seismic Love waves [Book Review]", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" } ], "abstract": "This monograph is devoted to a methodical mathematical study, using the spectral theory of\nlinear differential operations, of surface Love waves. The authors are affiliated with the Institute\nof Chemical Physics and the Institute of Physics of the Earth of the Academy of Sciences of the USSR.", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "1968-04", "series_number": "2", "volume": "58", "issue": "2", "pages": "748-749" }, { "id": "authors:02d4s-fmt29", "collection": "authors", "collection_id": "02d4s-fmt29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140507-140900962", "type": "article", "title": "Study of the Energy of the Free Oscillations of the Earth", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" } ], "abstract": "The energies of the radial, torsional, and spheroidal free oscillations for a Gutenberg model earth were studied. Each mode of oscillation has a characteristic radial distribution of elastic and kinetic energy that fixes the parts of the earth that contribute most heavily in determining a particular resonant frequency. An examination of the partitioning of energy among compressional, shear, and gravitational energy as a function of mode number and depth immediately explains the persistence of the purely radial mode compared with the other normal modes of the earth. Only the first few spheroidal modes are sensitive to the density of the inner core; they are particularly sensitive to the density of the outer part of the core. The low-order spheroidal modes also exhibit a rapid rise of potential energy near the base of the mantle; this rise will permit improved estimates of the velocity to be obtained in this region, which is difficult to examine with body waves. The tabulated results allow estimates to be made of the previously neglected energy contained in the free oscillations excited by large earthquakes. An estimate of the energy in the low-order spheroidal oscillations excited by the great Alaskan shock suggests a value of 10^(23) ergs over the period range from 450 to 830 sec, implying that the energy density increases toward high frequencies if the total energy in the earthquake was of the order of 10^(24)\u201310^(25) ergs.", "doi": "10.1029/JZ072i008p02155", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1967-04-15", "series_number": "8", "volume": "72", "issue": "8", "pages": "2155-2168" }, { "id": "authors:y3tnj-9b967", "collection": "authors", "collection_id": "y3tnj-9b967", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140430-084329530", "type": "article", "title": "The composition of the terrestrial planets", "author": [ { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" }, { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" } ], "abstract": "The mean atomic weight is a useful parameter with which to discuss the composition of the terrestrial planets. Using the density-pressure relationships of the earth and assigning a mean atomic weight to the mantle and core with the help of shock wave data, it is possible to construct a mass-mean density curve for planets of a given mean atomic weight.\n\nThe Mariner IV occultation experiment and recent telescopic measurements have provided new data for the radius of Mars which are in substantial agreement and yield a density for Mars between 3.96 and 4.10 g/cm^3. Planetary radar data have been processed to yield improved estimates of the radii and masses of Venus and Mercury. The corresponding densities are \u03f1 (Venus) = 5.27 and \u03f1 (Mercury) = 5.50 g/cm^3. These new determinations of density are used to estimate the mean atomic weight of the terrestrial planets. The results are Mars, 25.3 \u00b1 0.4; Venus. 26.4; Mercury, 36; and the moon 22.0. The mean atomic weight of the earth is 27.0. These results can be compared with the following representative values for meteorites and terrestrial rocks: igneous rocks, 21\u201322; carbonaceous chondrites, 23.4\u201324.0; ordinary chondrites 24.4; \"high iron\" chondrites, 25.1; enstatite chondrites, 25.6; and iron meteorites, 55.", "doi": "10.1016/0012-821X(67)90005-2", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1967", "series_number": "1", "volume": "3", "issue": "1", "pages": "19-24" }, { "id": "authors:brrp0-8ey50", "collection": "authors", "collection_id": "brrp0-8ey50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140801-124032272", "type": "article", "title": "Velocity filtering of seismic core phases", "author": [ { "family_name": "Hannon", "given_name": "W. J.", "clpid": "Hannon-H-J" }, { "family_name": "Kovach", "given_name": "R. L.", "clpid": "Kovach-R-L" } ], "abstract": "Recent studies have proposed complexities in the velocity-depth function for the region surrounding the inner core which require additional branches in the travel time curve for PKP in the epicentral range of 125\u00b0 to 160\u00b0. The proposed PKP arrivals can be separated on the basis of their apparent velocities, which range from 24 km/sec to 100 km/sec. Using the Tonto Forest array in Arizona coupled with adjoining LRSM stations in the western United States, an effective linear array of 400 km in size is attained. Data from several events in the distance range from 130\u00b0 to 160\u00b0 recorded on this array have been velocity filtered and show some evidence of two precursors to PKP in the distance range from 135\u00b0 to 143\u00b0 and at least one intermediate branch between PKP1 and PKP2 at distances greater than 143\u00b0. The results appear to support the velocity solution for the core proposed by Adams and Randall, although more data are required before a conclusive discrimination can be made between competing velocity models.", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "1966-04", "series_number": "2", "volume": "56", "issue": "2", "pages": "441-454" }, { "id": "authors:vazft-yhz69", "collection": "authors", "collection_id": "vazft-yhz69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140507-124553554", "type": "article", "title": "The Interiors of the Terrestrial Planets", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" } ], "abstract": "Conclusions regarding the internal constitution of the terrestrial planets are dependent on the assumption as to the nature of the earth's core. It has previously been supposed that if the terrestrial planets, Earth, Venus, and Mars, are of similar composition the material of the core must represent a phase change, but if the core material is chemically distinct the planets must differ in over-all chemical composition. An equation of state for the mantle and core based on recent free oscillation and shock wave data is used in developing models of the terrestrial planets. It is demonstrated that Earth, Venus, and Mars can be satisfied with the hypothesis of chemical uniformity and a chemically distinct iron-rich core, provided that the external radius of Mars is about 3310 km. The radius of Mars could be as large as 3325 km and could differ only slightly from the gross composition of the earth, i.e. 2% less iron. Astronomical data indicate that Mars must be an almost homogeneous body, but compositional identity with the earth can be maintained by mixing mantle and core material.", "doi": "10.1029/JZ070i012p02873", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1965-06-15", "series_number": "12", "volume": "70", "issue": "12", "pages": "2873-2882" }, { "id": "authors:ga7y2-02606", "collection": "authors", "collection_id": "ga7y2-02606", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140430-073408090", "type": "article", "title": "Attenuation of shear waves in the upper and lower mantle", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" } ], "abstract": "The attenuation of seismic waves is a direct measure of the absorption due to nonelastic processes in the earth. The well known difficulties in obtaining body wave amplitude decrement data have been avoided by studying the spectral ratios of multiple ScS and sScS phases from two deep focus earthquakes recorded at near normal incidence. The average Q, for shear, in the mantle is about 600 for the frequency range 0.015 to 0.07 cps. Assuming that equal radiation occurs upwards and downwards from the source the average Q for the upper 600 km of the mantle is determined to be about 200 and about 2200 for the rest of the mantle. The value for Q at the base of the mantle is at least 5000 for shear waves.", "doi": "10.1785/BSSA05406A1855", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "1964-12", "series_number": "6", "volume": "54", "issue": "6", "pages": "1855-1864" }, { "id": "authors:38hq2-m3h84", "collection": "authors", "collection_id": "38hq2-m3h84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140513-132357063", "type": "article", "title": "Attenuation in the Mantle and Rigidity of the Core From Multiply Reflected Core Phases", "author": [ { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" }, { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" } ], "abstract": "In 1956 Press reported on single and double reflections of shear waves at near\nnormal incidence from the earth's core and was able to estimate the average dissipation\nconstant of shear waves in the mantle and place an upper bound for the\nrigidity of the earth's outer core at the core-mantle boundary. However, because\nof excessive reverberations and the low sensitivity of the seismographs only a few\nusable seismograms were found in five years of continuous data. In this paper me\nreport on a seismogram showing unusually clear, near-vertical multiple reflections\nof shear waves from the earth's core. We have been able further to reduce the\nupper bound on the rigidity of the core, to estimate the average dissipation coefficient for 20-30 sec shear waves in the mantle, and to estimate the dissipation in the\nregions of the mantle above and below the earthquake focus. In addition, we have\nrecomputed the origin time and depth of focus from information contained in this\nsingle seismogram.", "doi": "10.1073/pnas.51.2.168", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1964-02", "series_number": "2", "volume": "51", "issue": "2", "pages": "168-172" }, { "id": "authors:yyrcj-2zt05", "collection": "authors", "collection_id": "yyrcj-2zt05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140429-152446765", "type": "article", "title": "Higher mode surface waves and their bearing on the structure of the earth's mantle", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" } ], "abstract": "A detailed numerical investigation of surface wave dispersion and particle motion associated with the higher Love and Rayleigh modes over realistic earth models has been carried out as a preliminary to the routine use of these waves in studies of the crust-mantle system. The suggestion that the so-called channel waves, such as the Lg, Li, and Sa phases, can be interpreted by higher mode group velocity dispersion curves is verified in detail. Furthermore, Sa should have a higher velocity across shield areas than across normal continental areas and a higher velocity across continents than across oceans.\n\nHigher mode Rayleigh wave data are presented for long oceanic paths to Pasadena. The observed data favor the CIT 11 model of Anderson and Toks\u00f6z (1963) over the 8099 model of Dorman et al. (1960) and indicate that under the Pacific Ocean the low-velocity zone extends to a depth perhaps as deep as 400 km followed by an abrupt increase in shear velocity.", "doi": "10.1785/BSSA0540010161", "issn": "0037-1106", "publisher": "Seismological Society of America", "publication": "Bulletin of the Seismological Society of America", "publication_date": "1964-02", "series_number": "1", "volume": "54", "issue": "1", "pages": "161-182" }, { "id": "authors:kza1f-y0j93", "collection": "authors", "collection_id": "kza1f-y0j93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140507-142020696", "type": "article", "title": "Long-Period Love Waves in a Heterogeneous, Spherical Earth", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Anderson", "given_name": "Don L.", "clpid": "Anderson-D-L" } ], "abstract": "Periods of torsional eigenvibrations have been computed for heterogeneous spheres corresponding to a variety of earth models, and the periods of oscillation are used to calculate phase and group velocities for the fundamental and first higher modes of Love waves. A comparison is made between velocities computed for different spherical models and for equivalent flat earth structures. The comparison shows (1) that the effect of sphericity is more complicated for fundamental mode Love waves than for Rayleigh waves because of the efficient channeling of waves by low-velocity layers and (2) that the first higher Love mode is more affected by curvature than the fundamental mode. The variation with depth of the relative amplitude of the displacements indicates that the first higher Love mode for periods less than 90 seconds is very sensitive to upper-mantle structure in the vicinity of the low-velocity zone. Comparison of the theoretical results with recent phase velocity and torsional oscillation data shows that a Gutenberg type of velocity structure is more satisfactory than either the Lehmann or Jeffreys structures. The use of consistent densities with the Gutenberg model, rather than Bullen A densities, has a small but significant effect on the calculated velocities. For periods greater than 200 seconds the calculated phase velocities for various oceanic and continental structures are all within 2 per cent of each other. The calculated group velocities are within 1\u00bd per cent of each other in the range 150 < T < 400 sec, thereby confirming experimental results. Dispersion measurements must therefore be made with precision if significant conclusions are to be inferred about details of earth structure.", "doi": "10.1029/JZ067i013p05243", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1962-12", "series_number": "13", "volume": "67", "issue": "13", "pages": "5243-5255" }, { "id": "authors:tktr9-pxc79", "collection": "authors", "collection_id": "tktr9-pxc79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141017-135944181", "type": "article", "title": "Geophysical investigations in the Colorado Delta Region", "author": [ { "family_name": "Kovach", "given_name": "Robert L.", "clpid": "Kovach-R-L" }, { "family_name": "Allen", "given_name": "Clarence R.", "clpid": "Allen-C-R" }, { "family_name": "Press", "given_name": "Frank", "clpid": "Press-F" } ], "abstract": "The combined approach of gravity and seismic refraction techniques was used to determine depths of the Cenozoic section and fault patterns of the Colorado delta region. Bouguer gravity anomalies range from \u221210 to \u221288 mgal with respect to the International Ellipsoid, and the trend of isogal contours is northwesterly. In the center of the basin, depths to basement estimated from gravity data are less than known minimum depths determined from seismic refraction profiles. This discrepancy suggests density complexities within the deeper parts of the stratigraphic section, an interpretation that is supported by sparse measurements from well samples; local isostatic compensation may also contribute to the discrepancy but is not thought to be the major cause. Measured seismic velocities ranged from 5650 to 20,000 ft/sec, and several consistent velocity zones were widespread above the pre-Tertiary basement; indicated depths to basement varied from 2200 feet to at least 15,400 feet, the greatest depth being near the international border. Many members of the San Andreas fault system are well delineated by gravity and seismic data, including the Elsinore and San Jacinto faults and a fault beneath the Sand Hills. Of these, the San Jacinto fault appears to be the most continuous through the delta region, but all appear to be en echelon to the trend of the San Andreas fault system as a whole.", "doi": "10.1029/JZ067i007p02845", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1962-07", "series_number": "7", "volume": "67", "issue": "7", "pages": "2845-2871" } ]